A drive is known from European EP-A 0,726,345 which is effective through transmission elements on a main drive shaft provided with a switching gear wheel. The switching gear wheel meshes in a first position with a gear wheel of at least one drive of the sley of the weaving machine and with a gear wheel at least for the drive of the shed forming means. In a second position the switching gear wheel meshes only with one of the two gear wheels.
A drive for a weaving machine is known from WO 98/31856. The drive of which is arranged coaxially to and directly coupled to the main drive shaft. The main drive shaft of the weaving machine is shiftable by a hydraulic or pneumatic adjustment system in one direction so that the drive power is applied only to the shed forming mechanism. Further, the main drive shaft is shiftable straight through the motor field in the opposite direction so that the drive is effective for the sley, possibly also for the grippers, as well as for the shed forming mechanism, i.e. this position of the main drive shaft is the position for the current weaving operation.
The above mentioned solutions start from a central drive and from an interlocking connection between the weaving machine and the shed forming machine in the weaving operation. Thus, all alternating moments are transmitted through the main drive shaft or at least through sections thereof. The resulting torsions cause vibrations which are transmitted onto the entire structure. Such vibrations may lead to impairments of the weaving quality. Such vibrations also have a high power consumption of the drive system and a high dead time frequency of the entire machine. Further, the interlocking connection between the weaving machine and the shed forming machine is subject to wear and tear as well as failure.
The above mentioned solutions are also disadvantageous with regard to the layout of the drive because the interlocking connection between the weaving machine and the shed forming machine require that both start simultaneously. As a result a very high start dynamic is required for avoiding start-up spots in the fabric. Such a high start-up dynamic requires drive motors with an extremely low inertia relative to their torque development. Such drives then have in most instances a thermal moment (rated moment) which is inadequate for a continuous operation so that external cooling is required, mostly with oil or water. A further disadvantage is, that the adjustment mechanisms provided in the known solutions for the switching gear wheel or respectively for the main drive shaft are additional components subject to wear and tear which additionally entail an extra maintenance effort and expense.
A drive mechanism for a weaving machine is already known from European Publication EP 0,893,525 A1, which drive mechanism comprises a weaving machine with a drive motor operating as a main motor or as an auxiliary motor, a shed forming machine with a drive motor operating correspondingly as auxiliary motor or as a main motor and a control device. The control device is constructed to follow a closed loop control strategy in order to operate the auxiliary drive relative to the main drive in a synchronous manner or with a leading or trailing angular position. The EP 0,893,525 A1 does not disclose how in such a drive mechanism fluctuations in the r.p.m. of the drive of the shed forming and weaving machine can be substantially compensated relative to the main shaft of the weaving machine and the drive shaft of the shed forming machine.
A method for driving a weaving machine is known from DE 44 36 424 A1, wherein the weaving machine main shaft is rotated with the aid of at least one electric motor drive that is coaxially connected with the main shaft. The electric motor drive is connected to a power supply network and is operatively connected with a control unit. The drive is operated by the control unit, preferably by sinusoidal control signals that are produced in the control unit in such a way that the main shaft, during a respective revolution, is rotated by the electric motor drive accelerated or decelerated with a variable rotational or angular velocity. The electric motor drive thereby is a d.c. drive which is so activated that it works at times as a d.c. motor and at times as a d.c. generator. In case the drive operates as a d.c. motor it is supplied with energy from a power supply network, and in the case that the drive operates as a d.c. generator, the electric energy produced by the drive is fed back into the power supply network.
Due to the fact that according to the known prior art, the weaving machine and the shed forming machine are driven substantially in synchronism during starting, it is necessary to provide a relatively high total energy by the power supply network during the starting phase. This circumstance is valid for weaving machines which are equipped with at least one main drive motor, whereby the drive for the shed forming machine is derived from the main drive shaft of the weaving machine. This circumstance is valid as well for weaving machines which are equipped with a drive mechanism according to EP 0,893,525 A1.